Ceiling supplies and Kohler K-303 Why Not?

I am remodeling a shower and will be installing a Kohler k-303 Three valve shower valve (Hot, Cold & diverter).
For some reason the instructions say that I cannot use this valve with ceiling supplies.
I could certainly re-route the copper and bring the supplies in from below, but, for the life of me I can't figure out why they say not to use the three valve yoke with ceiling supplies.
(The also make a two valve yoke {without the diverter} and there is no such warning for this one).
Any ideas?

Hate to burst your bubble, but unless I've overlooked it, that valve will NOT pass inspection on a remodel or new installation - it does not have the mandated anti-scald technology REQUIRED by code. Save yourself some hassles, ditch the Kohler, and install a different brand. Kohler changes their designs on a whim, and getting parts is really tough, not counting the code issues. They do make valves that will pass code if you decide to stay with them.

You are correct to a point.
Since I am replacing an existing 2 handle shower whose valves have gone bad, the city will let me install the valve in question.
If this were new construction, OR a major remodel you would be correct.
They will not force a homeowner to redo tile in a case like this.
So, my question remains....Why no ceiling supply?